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anyone have pictures and cliff notes of their performance disk brake conversions/installs?
Need more information on your setup, expected usage and budget.
I've got Ford Explorer discs on the rear that I did at the same time as the Dana axle swap. It was the cheapest disc brake kit I found at $350 complete, but required changing the housing ends on the axle. Since I was already having to do this using a full floating truck axle as a base it was no money lost.
The fronts on my car are just cross drilled/slotted 11.75" rotors with the factory single piston calipers. The rotors don't cost much, but you will need taller caliper brackets. All of this can be purchased from Doctor Diff. He specializes in Mopar brake kits and makes a lot of his own parts.
Overall impression of the above is it's good, but not what I'm looking for. Original idea was to make my own brackets and use a late model multi-piston caliper up front that wouldn't break the bank with the 11.75" rotors. I'm kind of leaning towards hyrdo-boost right now as I want to get rid of the vacuum brake booster on the firewall.
I’m leaning towards a big brake kit from wilwood up front and not sure if if I’ll stick with 11” drums or a disk conversion for the rear.
Budget wise, I have no issue spending money on things when I choose to.
Expected usage: nothing too crazy just looking for improved stopping and figure I’ll do a legit brake upgrade before I throw a 400 under the hood and things get squirrelly.
But are there folks here or on the web that made a conversion to disk brakes on a budget on the 7.1/4 or 8.1/4 for FMJ cars? I only can find gold dollar 4 piston caliper kits. If I have a template of making brackets for calipers and discs I can make it my self, but don't know if someone take it that way.
All FMJ cars came from factory with 11” front disks/10” rear drums OR with 11” front disks/11” rear drums (police/Taxi/trailer-tow cars).
To upgrade to 11” rear drum brakes, you need 11” backing plates, hardware, drums (get new drums) and parking brake cables (slightly different – but still available new via aftermarket). Getting the backing plates and drum hardware from most ½-ton pickups/vans is easy – but wheel/axle bolt pattern is different so drums will not work.
Note: 14” wheels will not work with 11” drums – you will need to upgrade to 15” or taller wheels.
To upgrade to 11¾” brake rotors is not hard to do. The brake caliper brackets from ’75-81 B and R-bodies is what you need and brake rotors (new rotors are still available). The caliper bracket to spindle bolts are longer – so make sure you get the bolts as well!
Note: there are two different ’75-81 B/R caliper brackets, pin type and slider type. All FMJ’s use slider type – so if you get slider type brackets, then existing brake pads/calipers can transfer over without much effort.
Note: 14” wheels will not work with 11¾” disks – you will need to upgrade to 15” or taller wheels.
There are two different Jeep rear disk brake setups that is a mostly easy change over. The Grand Cherokee and the Liberty. Both setups are similar but not the same. For what I hear, the Liberty system is a better, more cost-effective and easier to find system. Some modifications will need to be made to get parking brakes to work correctly.
I will be trying this and making a report afterwards.
From there is aftermarket front disk and aftermarket rear disk brake setups. I don’t have any experience about either to relay.
All I will say is brakes should be more important than engine, or anything else. If it won’t stop, it doesn’t matter how fast it gos. It might only be one acceleration that leads to a very bad day. We want our forum members to be around for a long time.
Dr.Diff has a kit, claims the 8 3/4 one will work if he modifies it a little.
I can't find the 11¾” brake rotors and bracket of the ’75-81 B and R-bodies online.
Found this set for 8.3/4" diff. Maybe making new brackets to fit a 7.1/4.
Speedway Mopar 8 3/4 in. Rear Disc Brake Kit for A, B, & E Body
Caliper brackets (B/R-body)
Mopar 11.75" Disc Brake Slider Caliper Brackets A very good price ($90 US). I’ve paid well over $100 for rusty used ones before.
The 11¾” brake rotors came on ’75-81 B and R-body (only). The wheel bearings (and spindles) are the same that FMJ’s use.
1977 DODGE CHARGER 6.6L 400cid V8 Rotor | RockAuto
These prices are in US dollars.
I have an easy way to tell if a car has 11” or 11¾” rotors on a car.
Look at the metal dust shield on back side of rotor. If the dust shield is noticeably wider/taller than the brake rotor, then you have 11” rotors.
If the installed brake rotor is about 3/8” (1 cm) taller than the dust shield, then you have 11¾” brake rotors.
This is a poor picture (FMJ suspension installed on an older pickup) – but does show the dust shield difference.
For loose brake rotors, look at area between the wheel mounting surface and rotor.
The FMJ rotors (11”) are (mostly) parallel. The 11¾” rotors are not. This is easy to see with them side by side. I have pictures taken of them side by side but not on this computer (sigh).
FMJ Rotor (11")
B/R-body rotor (11¾”)
Hopefully this helps,
If it fits an 8¾” differential, then it will also fit a 7¼” or 8¼” differential.
That statement will not work the other way around, though.
The kit you mentioned will fit and is not a bad price.
I’m leaning towards the Jeep Liberty rear disk brake setup, myself – but not sure about parts availability for you. As far as that goes, I’m not sure about replacement part availability (brake pads or rotors) for the above-mentioned kit, either.
I have take a look on the three different setups.
For the 11.3/4" ’75-81 B and R-body you can get the parts for around 260 dollar (rotor, calipers, pads, hoses and diff doctor brackets). Only these front type brakes supply no e-brake and so connection with cable. Also had to make a Axle Spacer Plate (spacer plate takes the place of the backing plate). And make a primary bracket to mount the Diff doctor bracket for mounting the calipers.
Jeep Liberty. Rotors on different sizes on years/front/rear (from 11.2" , 11.4" 12.45", 12"(front) etc). Some brackets for 8.25 Rear Axle, but which size rotor 2010 JEEP LIBERTY 3.7L V6 Caliper Bracket | RockAuto
If bracket should be good and can be build on the axle, there is no old style E-brake on the caliper (which I need it for MOT).
DBK834/DBK834LX 350$ kit.
Here a manual https://static.speedwaymotors.com/pdf/91664036.pdf
I did take a look for availability of spare parts or build up without the kit.
Most parts are sold separately. Even by common web shops.
Total price without brackets and bolts would be around 260$.
If add the doctor diff 10.95" brackets it would be 310$. But then you need to make your own Axle Spacer Plate (spacer plate takes the place of the backing plate). And make a primary bracket to mount the Diff doctor bracket for mounting the calipers.
There is also a hardware kit from Jegs from 130$. But then it getting around 400$. But have to say this is included with a F body E-brake cable set(I almost think that you can use this one for when removing the spring on the cable).
5560-834 - 1962-1972 Mopar A, B, & E Rear Plain Rotor (Passenger or Drivers)
1979 CADILLAC ELDORADO 5.7L 350cid V8 Caliper | RockAuto
1980 CHEVROLET MALIBU 5.7L 350cid V8 Brake Pad | RockAuto
Mopar 10.95" Disc Brake Slider Caliper Brackets
1979 CADILLAC ELDORADO 5.7L 350cid V8 Hydraulic Hose | RockAuto
E-Brake (the $$ option )
Disc Brake Emergency Brake Cable Set for 66-70 B-Body - Bouchillon Performance Engineering
1979 CADILLAC ELDORADO 5.7L 350cid V8 Hydraulic Hose to Caliper / Banjo Bolt | RockAuto
JEGS 630668: Rear Disc Brake Conversion Hardware Kit for Mopar 8 3/4 in.(A, B, E Body) and Dana 60 | JEGS
View attachment 37890
This is what the Liberty with rear disk brakes caliper bracket looks like (picture swiped from eBay).
This company wants $424 (US) for the new one (each), but a pair of good used ones can be found in the $20-70 (US) range.
what are the mods needed to fit the Jeep backing plates? Does any material need to be removed from the plate or is it an elongating of a bolt hole, something like that?
The Liberty ones are direct bolt on, they come off a Chrysler 8.25" rear. The Grand Cherokee ones need the center bore sanded to fit.
2005 JEEP LIBERTY 3.7L V6 Brake Backing Plate | RockAuto
Set of new ones. You needed parkingbrake hardwarekit + shoes.
you would also need the brackets, those are just the sheetmetal part
What years should I/we/people look for, for the rear disk brake assemblies from the Jeep Liberty's and Grand Cherokee's?
94-98 Grand Cherokee. 03-07 Liberty I think
Awsome! Thank you
Yes, what @80mirada said.
A few notes that need to be made:
The Grand Cherokee and Liberty both use solid brake rotors. For what I hear the Grand Cherokee version are not as trouble free (warp more often) as the Liberty system uses. Also, the Liberty rotor appears to be on store shelves more than the Grand Cherokee is (just relaying what I’ve heard – no firsthand experience with either).
Grand Cherokee (rear)
They both look similar, but will not interchange.
The Grand Cherokee bracket has a smaller center hub (and a smaller wheel bearing) and the center hub needs to be ground out a bit so it will fit. The bolt holes will keep it lined up – so no worry if you egg-shape the hole when grinding.
The Liberty system is almost plug and play system and appear to be the preferred changeover system of the two. Not all Liberty’s have rear disk brakes. If you find a Liberty with rear disks, then it will work. I think 8 out of every 10 Liberty’s have rear disk brakes.
The main part, the disk bracket (inner and outer view). This is the Liberty and the Grand Cherokee is similar.
Both the Grand Cherokee and Liberty uses 4-studs/nuts to attach to differential where as most (but not all) FMJ 7¼” and 8¼” differentials use 5-studs/nuts. I have seen a few FMJ’s made with 4 but most have 5 (I think early Monday (hungover) or late Friday (eager to get off and get drunk) – might be the reason).
Sense most FMJ’s have 5-holes, you most likely will need to drill a new hole for bottom most stud. If you drill a size bigger than other ones, then you won’t have to worry about getting it in exact position.
Example of 5-hole pattern.
Example of 4-hole pattern. This is actually a Liberty 10" drum brake backing plate. The top 4 holes line up exactly.
The axle shafts will have to be removed to install the plates and axles re-installed after plates are attached. The method to remove/install axle shafts are different between early 7¼” and late 7¼”/8¼” differentials.
For the late 7¼”/8¼”, you need to remove the inspection cover, remove the pin bolt, slide pin put. Push both axle shafts inwards enough to allow C-clip to come out and pull axles out. Reinstall in the same fashion.
Note: Inspect axle shafts for bearing damage on each axle shaft. If there is any discoloration of shaft or you can catch a fingernail on surface where bearing rides at, you will need to the replace wheel bearings. They now make offset wheel bearings (axle savers) which will allow you to reuse existing axle. Also plan on changing the axle seals when axles are out!
Now the early 7¼” differentials are different from late ones as well as the method to remove the axle shafts. The early means those made from ’76 to mid-year ’80 and have a 2½” diameter axle tube. The mid-year ’80 to 89 7¼” have a 3” tapered tube – which looks like this:
The ’76 to mid-year ’80 7¼” (with the 2½” differential tubes), the axle is removed much like the older 8¾” axles are, via unbolting the axle bearing retainer flange (at the brake backing plate).
This retainer plate will cause the disk brake plate to extend outwards more than usual that could cause abnormal brake pad wear. This problem is the same exact problem that older 8¾” differentials have. The fix for them is to machine the plate down the thickness of the plate (just a smidge more than 0.1” (one tenth of an inch), on both plates. A possible fix would be to make and install a spacer (of 0.1”) and place between the axle flanges and brake rotors. If you do make a spacer, make sure it not just washers but a shim the size of the axle flange. Washers only will contribute to brake rotor warpage.
Example of a shim/spacer.
Another problem with using an older 8¾” or early FMJ 7¼” differential is the wheel bearing will need removed (replaced)m have bracket installed, and wheel bearing installed which will sandwich the plate between the axle flange and wheel bearing retainer.
This does not affect the 8¼” differential at all, nor the mid-year 1980-89 7¼” differentials.
One other thing to keep in mind is the parking brake cable attachment is different!
I ran of room for pictures on above post.
This is a picture of how factory setup the Liberty rear disk brakes. There is a pair of hoses between the calipers and metal brake lines. A few people ran hard lines to the calipers. I don’t have a problem with that, but it does make changing brake pads (or other differential work) more difficult in the future. If the hoses are left in place, then brake pad replacement is pretty easy. Bending the brake lines on a hard-line attachment and back again is a no-no.
Note: Chrysler axles have a hole drilled into them to allow a person to access the nuts using a socket wrench (or impact).